POWER AMPLIFIER
1000
FEATURES
◆
2 x 350 W into 8
Ω
2 x 550 W into 4
Ω
2 x 675 W into 2
Ω
at clip level with both
channels driven
◆
Compact design, 2 U high
(88 mm)
◆
Low weight
◆
Electronically balanced
inputs
◆
LED indicators show output
voltage and headroom
◆
Independent protection
circuitry
◆
Manages long-term short-
circuit operations
◆
VHF protection
◆
DC protection
◆
Output cooled by Intercooler
®
◆
Two proportional speed fans
◆
Clip limiter
LAB. GRUPPEN’s LAB 1000 is a high
power amplifier, designed for 19”
rack mounting.
The 2 U (units) high welded chassis
is made of 2 mm thick steel plate.
The power transformer is of a two-
coil low-loss type, mounted just be-
hind the front panel, which gives the
LAB 1000 a stable and balanced de-
sign. Both the power supply and the
two output channels are cooled by
two proportional speed fans, where
the air flows from front to back.
Twenty 250 watt bipolar power
transistors constitute the output
stages, which are totally complimen-
tary. The power transistors are
cooled by a solid copper cooler, called
Intercooler(r), originally designed for
our SS 1300 power amplifier. LAB.
GRUPPEN’s specially designed ther-
mal feedback circuit protects against
thermal breakdown.
The output stage is designed total-
ly discreet, to get the best optimisa-
tion for linearity and bandwidth. The
driver stage consists of an “enhanced
cascode circuit”, which is differential
symmetrical in class A, to achieve low
distortion at high frequencies. The
circuit was originally developed by
LAB. GRUPPEN in 1980, and experi-
ence has proven that this design gives
the power amplifier high reliability.
The LAB 1000 is completely short-
circuit protected - even in reactive
loads. The LAB 1000 is equipped
with LAB. GRUPPEN’s specially de-
signed short circuit protection, which
permits very high peak-currents, but
still holds the transistors within the
so-called “Safe Operation Area”. This
makes it possible to run loudspeakers
with impedance variations, which are
considerably lower than the lowest
permitted impedance of the power
amplifier.
Four more protection circuits,
which are separate for each channel,
protect the LAB 1000 and the loud-
speakers:
Two DC protections;
one DC cur-
rent limitation protection, supple-
mented with fuses on each DC volt-
age power supply rail; and one DC
voltage protection of Crowbar type,
which works by short-circuiting the
output to protect the load.
Thermal protection;
prevents the
LAB 1000 from being overheated.
The temperature indicators on the
front panel are switched on, as a
warning, before the protection oc-
curs.
VHF protection
(Very High Fre-
quency); protects the loudspeakers
against strong non-musical signals
above the audible area.
Clip limiter;
prevents severely
clipped waveformss from reaching
the loud-
speakers, but maintains full peak
power.
All electronics are mounted on two
modules, one for channel A and one
for channel B. The modules are easily
accessible for replacement or repair,
etc.